High speed tool steel



June 18, 1968 Filed Aug. 9, 1965 HARONESS 5 Sheets-Sheet 2 ROOM TEMP so N EFFECT OF HARDENING 58 AND TEMPERING TEMPERATURES ON THE HARDNESS AT HEAT 248 56 HARDENING ram s ZIOO'F 54 ZZOO'F C Mn Cr W V Mo Co m2 O'3l 4-32 6-58 r99 3-83 4-70 50 TEMPERING TEMF?--- I000 n00 I200 FIG.2

Jul-1e 1968 w. B. F. MACKAY ETAL 3,388,986

HIGH SPEED TOOL STEEL Filed Aug. 9, 1965 5 Sheets$heet 5 I I l Tu rnlnq H-ll Hot Work Die Stel Quenched nd Tempered 50 Re With Eight Atlas HSS Tools Tool Moteriol: HSS (See below) 80 Test Stopped Tool Geometry:

.032" weorlond BR: 0 SR: |o SCEA: l ECEA: 5 Reliefi 5 NR: .030" Feed: .009 in. /rev. 70 Depth of cm: .062"

QCuHinq Fluid: Soluble Oll (I220) Tool Life End Point: .060

' Weorlond I) Tool 245 3 o 5 .E E I 40 m t I 0 Tool M=34 10 Tool his Cutting Speed feet/minute FIG. 3

United States Patent 3,388,986 HIGH SPEED TOGL STEEL William B. F. Mackay, 21 Haist Road N., and Robert 0. tiarson, 81 Carboro Road, both of Fonthill, 0ntario, Canada Filed Aug. 9, 1965, Ser. No. 478,116 Claims priority, application Canada, June 4, 1965, 932,496 4 Claims. (Cl. 75-126) ABSTRACT OF THE DISCLDSURE A high speed tool steel which in its hardening state has improved hardness suitably of the order of R 70 hardness and thus improved wear resistance as well as improved toughness which steel consists of, on a percentage basis, 1.15 to 1.25 carbon, 4.00 to 4.5 chromium, 4.25 to 5.00 tungsten, 1.85 to 2.15 vanadium, 6.75 to 7.75 cobalt, 7.00 to 8.00 molybdenum, .20 to .40 manganese and .15 to .45 silicon, the balance being iron and residual impurities.

This invention relates to a new and improved steel composition and more particularly to a steel composition especially adapted for tool steels employed in high speed operations.

Among the properties which are desired for high speed tool steels are versatility, low ingot cost, suitable grindability, workability and response to heat treatment, and adequate tool life as related to heavy cutting and high speed machining and measured in terms of red hardness and abrasion resistance. Tungsten, molybdenum, vanadium, chromium and cobalt are the alloying elements found in these steels.

it is an object of this invention to provide a tool steel having high speed machining features superior to present steel compositions while still maintaining properties of versatility, suitable grindability, and workability and adequate response to heat treatment.

Other objects of the invention will become apparent from the description to follow:

The objects of this invention are attained in a tool The balance iron plus residual impurities.

Some preferred percentage compositions were analysed as follows:

C Mn Si P S C! W V M0 Co The balance iron plus residual impurities.

Car

Phosphorus and sulfur are considered as impurities at their low levels, the manganese being employed to reduce the harmful effects of sulfur on the hot workability of the steel.

A preferred heat treatment of the steel includes a preheat step of 1500-1550 F. followed by hardening at 2175-2225 F. with a recommended temperature being 2200 F. The material is then tempered at from 95 0-1200 F. with maximum hardness produced by a triple temper at 975102'5 F. with 2 hours of each temper.

An induction heat (H245) having the composition in preferred analysis No. 1 was meled, cast and processed to tool bit size for a comparative evaluation with the tool steel (H248) described in US. Patent 2,996,376. This latter composition analysed as follows:

Some of the test data are graphically illustrated in FIG- URES 1-3.

TOUGHNESS COMPARISONS Un-notched izods were prepared by fully heat treating oversize bars, then carefully finish grinding in the hardened condition using a soft wheel and low metal removal rate. All specimens were magnafluxed prior to testing.

The results are shown below and it will be noted that H245 is marginally superior to H248.

Heat No. Hardness Uri-notched Izod Impact ArIrerage zod Strength Values H245 69. 5 6622.555-961322 10. 5 H248 6S. 5 11-8-8-11-10-9 9. 5

TOOL LIFE TESTS Four sets of tool steels were cut from /8" square annealed stock. Two sets which were used corresponded to the analysis of H245 and H248. The other two tool steels analysed as follows:

C Mn Si Cr W V Mo C0 A.1.S.1. T-15 1.25 .30 .39 4.25 10.00 4. 30 2 50 5. 50 11.1.5.1. M-34 90 30 25 3. 75 1. 45 2. 05 8 8. 25

The tools ground from these grades had the following dimensions:

Back rake degrees 0 Side rake do 10 Side cutting edge angle do 15 End cutting edge angle do 5 Relief "do"--. 5 -Nose radius inches .030

A.1.S.1. H-ll was the material used to rate the tools. A 3" diameter rod, 15" long of H-ll was quenched and tempered at 50 R Tool life was then measured against cutting speeds and the results are shown in FIG. 3. It will be observed that composition H245 has about twice the wear life of H248.

3 HARDNESS COMPARISONS (1) Room temperature hardness.Samples about /2" x /2" x 1" were cut from the 4 /4" R sq. billets. Samples were salt hardened from 2100, 2150, 2200, 2250, 2300 and 2350 F., interrupt quenched at 1050 F. subsequently double tempered (2 hours each) at 1000, 1100 and 1200 F. The resultant hardness shown in It will be observed that on the basis of the above-noted tests, H245 is superior in hot hardness and grindability, and markedly better in tool life than H248, while still maintaining equivalent toughness to H248.

We claim:

1. A high speed tool steel having the following percentage composition:

FIGURES 1 and 2 indicate that the optimum hardening C M5425 temperature is in the range 2200-2250 F. Hardness of 400450 68-69 R was obtained on both compositions after hard- W 4 O0 ening and then tempering at 1000 F. Applicants analy- V sis (H245) offers the most resistance to tempering, when CO 6 75 hardened from 2250 R, which indicates superior hard- MO 1185s- 15 M (2) Hot hardness.-A second hardness evaluation was l g: determined by heat treating four samples: H245, H248, T-15 and M-34 and subjecting them to hot hardness tests. The heat treatment for H245, H248 and M-34 were as The f j Plus resldual follows: 2. A hlgn speed tool steel having the following percentage composition: c 1.20 Preheat 1500-1550 Mn Salt harden 2190-2210 Si Salt interrupt 1050 m p Double draw 2 hrs.+2 hrs. at 1025 F. S .010

C T-15 was given a heat treatment at somewhat higher temperatures as follow v 230. F. 30 Mo 7.62 Preheat 1550-1600 Co 734 Salt harden 2225-2250 Salt interrupt 1050 The balance iron plus residual impurities, the latter in- Double draw 2 hrs.+2hrs. at 1025 F. eluding lf and phosphorus 3- 3.Ah'h edtltlh The results of the heat treatment tests were as follows: 0 cgntage i z i S ee avmg the following Per HOT HARDNESS Temperature at Test, F. H245 H248 M34 T15 5 70.0 68.0 66.0 68.0 40

62.7 62.5 60.5 61.8 1 P m3 as an in c fit I 58.8 51.2 56.1 55.7 Y W 457 v 2.07 Grindability.Samples of H245 and H248 were tested Mo 750 under the following conditions: Co 7.20

Machine i g zz g gggf 5 '1;hei ba1ani:fe irondpltlils regidual impurities, the latter incu mg su ur an p osp orus. 123 g ii i jlzii: E 2 52 4. A high speed tool steel having the following percent- Wheel speed 3500 r.p.m. age P= Material ground Various kinds as shown V below (2" X area). C 112 Grinding fluid None-dry grinding. M .29 Table speed f.p.m. S1 .42 Crossfeed .060" per table reverse. P .014 Infeed per pass .003". S .010 Number of passes 150. C0 C1 4 32 Dressing technique Open--.001 per pass until W 4.52 wheel trued up. V 2.02 Mo 7.64 Co 7.34

The following results were obtained:

Ratio of weight Material Ground Metal Removed Wheel ofmetalre- Finish Load Check Number Rock- Loss, moved/weight Ml, Burn on on well Inches Grams Grams of wheel RMS Wheel Steel removed 11245 C 07 .437 74.54 5.90 12.6 85 LL. Brown... Some... No. 11248.... c 68 .428 71.14 8.30 8.6 Till] Light No.

The balance iron plus residual impurities, the latter including sulfur and phosphorus.

References Cited UNITED STATES PATENTS Emmons 75126 Nehrenberg et a1. 75126 Harvey et a1 75126 Hamaker et a1. 75126 6 FOREIGN PATENTS 8/1955 Australia.

OTHER REFERENCES 10 CHARLES N. LOVELL, Primary Examiner. 

